Strip accumulator

ABSTRACT

A method of storing a variable amount of strip in a continuous strip-feeding system adapted to allow variation of the rate of feed-in in relation to the rate of withdrawal, comprises forming the strip into a spiral coil having a constant number of turns and having its axis vertical, rotating the coil and feeding incoming strip onto the inside of the coil, withdrawing strip from the outside of the coil.

United States Patent 1191 Bradshaw Jan. 14, 1975 [5 STRIP ACCUMULATOR 3,218,000 11/1965 Blackman 1. 242/78.l 3,258,212 6/1966 LaTour v 242/781 X [75] Inventor- 9"? Bradshaw 3,506,210 4/1970 LaTour 242/55 Blrmmgham, England 3,628,742 12/1971 Fritzsche 242/55 [73] Assignee: Tube Products Limited, Oldbury,

Warley, Engl d Primary Examiner-John W. Huckert Assistant Examiner-Edward J. McCarthy [22] Flled: 1972 Attorney, Agent, or FirmScrivener Parker Scrivener [2]] Appl. No.: 317,178 and Cla ke [30] Foreign Application Priority Data [57] ABSTRACT Dec. 21, 1971 Great Britain 59446/71 A method of storing a ab e amount of s rip in a continuous strip-feeding system adapted to allow vari- [52] us. Cl. 242/55.21, 242/78.l ation of the t of d-i i relati n to the rate of [51] Int. Cl B65h 17/48 al, c mprises forming the strip into a spiral [58] Field 61 Search 242/55, 55.21, 78.1 coil having a constant number of turns and having its axis vertical, rotating the coil and feeding incoming [56] References Cit d strip onto the inside of the coil, withdrawing strip from the outside Of the coil.

2,037,601 4/1936 Shirlow 242/5521 11 Claims, 7 Drawing Figures PATENTEDJANWBYB I Y 3.860.188

' sum no; 4

STRIP ACCUMULATOR This invention relates to a novel form of strip accumulator, that is to say, means for storing strip being fed from a source of supply, such as a coil of strip, to a machine or other apparatus which processes or uses the strip, so that the machine or other apparatus can be kept running without interruption whilst the source is replenished. Such a need arises in mills for forming continuously welded metal tube from flat strip, where it is important to keep the tube forming and welding machine running continuously while the leading end of a new coil of strip is being welded onto the tail of the preceding coil. Known accumulators involve the strip, as it is taken off the coil, being led back and forth in a series of loops, vertical or horizontal, carried over rollers that are normally spaced a substantial distance apart but can close up to yield the strip stored in the loops. These systems take up a lot of space and are complicated.

Several attempts have been made to use a system in which a coil is formed of the strip, mounted with its plane vertical, with fresh strip being fed onto the outside of the coil whilst strip is taken off the inside of the coil for feeding to the mills.

Other known systems have involved the use of two coils, one inside the other or one above the other or .side by side, the coils being wound in opposite senses,

and one or more turns the strip being added to or removed from both coils simultaneously to increase or decrease the total stored. Such systems are described in US. Pat. No. 3,310,255 of Sendzimir. In them the mean diameter of each coil remains substantially constant. The chief drawback of these systems is their complexity and in some versions the strip is subjected to severe bending in its transfer from one coil to the other.

The aim of the present invention is to provide a new form of strip accumulator that is simple and reliable in operation, and easy to control. According to the invention in its broadest aspect we propose a method of feeding strip material to a process while providing a variable reserve to allow for intermittent interruptions of the feed-in and or withdrawal of the strip while maintaining the withdrawal of feed-in respectively, comprising forming the strip into a single spiral coil having a fixed number of turns and having its axis substantially vertical, feeding the strip onto the inside of the coil while withdrawing the strip from the outside of the coil, defining the maximum and minimum radii which the turns of the coil are allowed to have, the difference between these radii being greater than the radial space occupied by the given number of turns of the coil when those turns are close-packed, and allowing the turns to contract successively, or expand successively, to provide a reserve represented by the difference between the expanded and contracted circumferential lengths of the turns that allows continued withdrawal in the absence of feed-in or continued feed-in in the absence of withdrawal, up to the limit of the number of turns present.

A strip accumulator for carrying out this method comprises a table designed to support a single spiral coil of strip with its axis substantially vertical and including means for rotating the coil about its axis and for guiding strip onto the inside of the coil and guiding strip off the outside of the coil, and means defining the inner and outer limits of the radius of the coil, the arrangement being such that when the in-feed of strip stops, the strip can continue to be withdrawn from the coil, the number of turns on the coil then remaining constant but their mean diameter decreasing.

In this way the problem of providing a reserve of strip to allow a continuous withdrawal whilst intermittently stopping the feed-in is overcome with a single coil by allowing the reserve to come from the reduction in diameter, but not in number, of the turns of strip present in the coil. Then when the feed-in is resumed one can build up a fresh reserve by feeding strip in at a rate faster than that at which it is being withdrawn, so that the turns once again increase in diameter.

By feeding onto the inside of the coil and withdrawing strip from the outside we ensure that the strip is curved to its greatest degree of curvature initially, and this curvature decreases progressively as it moves to the outside of the coil. Consequently the behaviour is much smoother and more predictable than if the strip were to be fed onto the outside and withdrawn from the inside.

By arranging the coil with its axis of rotation vertical we avoid the problems, found with coils set on edge, of the coil becoming egg-shaped or otherwise distorted by gravity. Preferably the table is not a single rotary platform but is formed by an array of radially extending, or nearly radially extending, rollers. According to a subsidiary feature of the invention these rollers do not have their axes horizontal but have their inner ends higher than their outer ends so that they define a table which is slightly conical. They therefore tend to urge the turns outwards, i.e., towards their maximum diameter. Some or all of the rollers are powerdriven to rotate the coil.

The invention will now be further described by way of example with reference to the accompanying drawings, in which:

FIGS. 1 and 2 are diagrammatic plan views of a coil to illustrate the principle behind the invention;

FIG. 3 is a plan view of a practical form of the invention, showing the apparatus loaded to its maximum capacity;

FIG. 4 shows the apparatus of FIG. 3 with the feed-in stopped and the strip continuing to be withdrawn from the coil;

FIG. 5 shows the same apparatus at is minimum capacity, i.e. after the maximum permissible amount of reserve strip has been withdrawn from the coil;

FIG. 6 is a vertical section, in a plane containing the axis of the coil, through one side of a modified form of the apparatus of FIGS. 3, 4 and 5; and

FIG. 7 is a diagrammatic plan view showing a modified form of feed-in.

Referring first to FIG. 1, it will be seen that, if a strip 1 of material, for example steel strip to be fed to a tubemaking mill, is formed into a coil 2 of several turns and the incoming strip is fed through rollers 3 onto the inside of the coil while'the out-going strip, passing to the mill, is taken simultaneously from the outside of the coil through rollers 4 while the coil is rotated, the number of turns on the coil will remain constant. If the rate of feed-in is equal to the rate of feed-out the dynamic conditions remain constant. The innermost turn is turning slightly faster than the outermost turn, so that their circumferential speeds remain equal. The maximum diameter of the outermost turn is determined by a set of guide rollers 5.

If now the feed-in is halted, for example to allow the leading end of a new strip to be welded to the tail end of the strip that is passing through the coil, it is possible to continue rotating the coil and withdrawing strip from the outside of the coil and passing it to the mill. The number of turns in the coil cannot change but their diameter does; the innermost turn contracts until it engages a set of rollers 6 that determines its minimum diameter, followed by the next turn and so on, until we reach the condition shown in FIG. 2, where all the turns have contracted down to their minimum diameter. The total reserve. of strip yielded up in this way is equal to the number of turns multiplied by the difference between the mean peripheral length of the turns in the condition shown in FIG. 1 and the mean peripheral length of the turns in the condition shown in FIG. 2. As long as the coil is positively rotated, i.e., we are not merely pulling the strip off the outside and letting the turns rub over one another, friction is no problem, and the change in diameter from maximum to minimum starts with the innermost turn, ending with the outermost turn.

It will be understood that, before the condition shown in FIG. 2 is reached, the feed-in must be resumed. It can be resumed at a linear rate higher than the rate of withdrawal. In fact at this stage it would be possible to continue the feeding in even with the withdrawal halted altogether, so the invention is applicable equally well where the withdrawal, as well as or instead of the feed-in is liable to be interrupted. The feed-in can be allowed to overtake the withdrawal until we have once again reached the conditions shown in FIG. 1. By rotating the coil at an appropriate speed we can again ensure that friction between the turns is no problem, as change from minimum to maximum can be caused to start with the outermost turn and end with the innermost turn.

FIGS. 3, 4 and 5 are plan views of a practical embodiment. A supporting table by which the coil is rotated is formed by an array of twelve long thin cylindrical rollers 7 mounted in pairs. In the example illustrated all the rollers are positively driven by individual variablespeed electric motors (one of which is indicated diagrammatically at M in FIG. 3) but in a modification some of the rollers'could be idlers, or there could be additional idler rollers between the adjacent driven pairs. In a further modification the idler rollers could be shorter than the driven ones, for example only half their length or less, and extend inwards from the outer periphery of the table to stop well short of its centre.

By the use of cylindrical rollers of uniform diameter, instead of a single table and instead of tapered rollers, we ensure that the strip is driven at a uniform linear speed regardless of the diameter of the turn which it occupies at any given instant.

The axes of the rollers are shown as being very nearly 'truly radial with respect to the axis of the coil. However so that they slope slightly downwards and outwards to define a slightly conicalsupporting surface rather than a flat one. This serves the same purpose as the skewing,

i.e., to urge the turn radially outwards as they rotate.

The feed-in rollers 3 and the withdrawing rollers 4 are also indpendently driven by respective variable speed electric motors. The maximum diameter of the coil is defined by a ring of idler rollers 5. To define the minimum diameter there is a spider 8 mounted above the table and having four arms, on each one of which a respective idler roller 6 is mounted to be radially movable between an inner position (shown in FIG. 3) and an outer position (shown in FIG. 4). Also mounted above the table is a bridge 9 on which are mounted pinch rollers 10 for the incoming strip, which comes in horizontally above the coil and then spirals down to the level of the coil. The bridge 9 is shown partially broken away in FIGS. 3, 4 and 5 to reveal the spider 8.

FIG. 3 shows the table carrying its maximum capacity, which in the example shown is turns, and they are at their maximum diameter. It will be understood that the number of turns to be used will depend on the gauge of the strip and the reserve capacity required.

To load the apparatus initially the leading edge of the strip is fed through the rollers 3 and 10 and guided round to form a single turn of nearly the maximum diameter, the end of the strip being then temporarily tack-welded to the outer surface of the next turn. Then with the feed-in rollers 10 and the table rollers 7 all simultaneously driven at their correct relative speeds, 100 turns of strip are wound in. The tack weld is broken and the leading end of the strip taken out through the withdrawal rollers 4. With these rollers stationary or only rotating slowly, so that the withdrawal is slower than the feed-in, the coil is rotated by the rollers 7. The outermost turn, because its withdrawal is slow or nonexistent, increases in diameter until it lies fully against the ring of idler rollers 5, followed by the next turn, then the next and so on untilwe reach the condition shown in FIG. 3.

The strip accumulator is then ready for operation. The feed-in rollers 3, the supporting rollers 7 and the withdrawal rollers 4 are all driven in synchronism to give the same linear speed and the coil rotated, but the dynamic conditions remain constant. The inner rollers 6 are moved to their outermost positions, shown in FIG. 4. This state of affairs continues until the tail end of the strip is approaching the feed-in rollers 3. At this moment the drive to the feed-in rollers is stopped, but the supporting rollers 7 as well as the withdrawal rollers 4 carry on. As a result the innermost turn of the coil contracts until its contraction is limited by the rollers 6. This condiition is shown in FIG. 4. Then the next turn follows, and so on, the coil continuing to rotate in the meantime or at least those turns of the coil that have not yet contracted. Eventually, unless the feed-in resumed in time (the leading end of a new strip having been welded to the tail end of the strip that forms the coil) the outermost turn will contract onto the remain der and the coil will be unable to supply any more strip. FIG. 5 shows this condition about to be reached. If this state of affairs is reached the mill will suddenly be in trouble and the strip may break and so we preferably provide an emergency stop in the form of four limit switches (not shown) spaced around the periphery of the table between the rollers 5 and kept closed by the presence of the outermost turn of the coil. As soon as any one of these switches is opened, indicated that the outermost turn is starting to contract and so the reserve is used up, the power to the mill is cut off.

In normal operation this state of affairs will not be reached and the size of the strip accumulator will be selected, in relation to the speed of the mill and the gauge of the strip as well as the time taken to weld on a new strip, to give an ample margin of safety. It will be understood that the minimum diameter to which the strip can be coiled, i.e., the circle defined by the rollers 6 in their outermost positions, is determined not only by the gauge of the strip but also by its width, since it will be difficult to feed a very wide strip in the necessary spiral path into the centre of the coil if the centre is unduly small.

The radial positions of the pair of pinch rollers on the bridge 9 is preferably adjustable in step with the movement of the rollers 6, as will be seen by comparing FIGS. 3 and 4. These rollers may be arranged to impart a deliberate curvature to the strip to help if fit snugly into the coil.

After the feed-in has been halted and the reserve is being used the rollers 6 and pinch rollers 10 can be returned to their radially innermost positions.

When the feed-in is resumed, the feed-in rollers 3 and also the supporting rollers 7 can be speeded up to a lincar speed higher than that of the withdrawal rollers (whose speed is governed by the mill to which the strip is fed). Consequently the outermost one of those turns of the coil which had contracted will overtake the outer turns and will expand to lie against the inner one of them, followed by the next, and so on, until the whole coil resumes the condition shown in FIG. 3, holding the maximum reserve ready for the next interruption of the feed-in.

In a modification the outer rollers 5 could be omitted, replaced simply by a fixed peripheral wall. Also it may be possible to combine the pinch rollers 10 with one of the inner rollers 6, i.e., to use one of the rollers 6 as a pinch roller. A further possibility is to replace the ring of rollers 6 by a complete drum or winch rotatable about the axis of the table by a drive independent of that of the supporting rollers 7.

Yet another variation is shown in FIG. 6 which is a vertical section, on one side of the axis, through a modified construction in which the rollers 6 carried on a spider 8 are replaced by a ring of rollers, of which one is visible at 6', on fixed axes. This version also has the outer rollers 5 replaced by a fixed wall 11. ln addition there are a number of angular spaced skids 12, for example four, between the rollers 7, pivoted at their outer ends at points 13 near the periphery of the table and having their inner ends capable of being lifted by pneumatic rams 14. When the rams are energised a surface 15 on each skid lifts the inner-most turns of the coil off the rollers 7 and, because of the inclination of the sur faces 15, these turns are encouraged to expand radially. The skids 12 are lifted before feed-in is resumed after a halt, and this helps in the expansion of the contracted turns to build up the reserve again. In place of the surfaces 15 the skids 12 could have rollers to reduce frictron.

A further possibility is to make either the inner or the outer ends of the main supporting rollers 7 adjustable in height, for example under the control of pneumatic rams, to alter the inclination of these rollers according to the state of the coil. This is indicated diagrammatically by the ram 14' shown in broken lines in FIG. 6.

FIG. 7 shows diagrammatically a modified form of feed-in, in which the pinch rollers 10' are mounted on the free end of an arm 16 which is pivoted about a vertical axis 17 outside the coil and can swing about this axis to deliver the incoming strip to the table at a smaller or larger radius, as required. As shown, the feed-in rollers 3' are also mounted on this arm, near its pivotal axis. The arm may be biased to swing outwards, for example by inclining its pivotal axis with respect to the vertical, or by applying external loading. As in the arrangements described above, rollers at the free end of the arm may be arranged to impart a curvature to the strip as it leaves the arm and enters the coil 2. The movement of the strip along the arm may be assisted by clamping the strip between two parallel moving belts running over rollers at the inner and outer ends of the arm.

I claim:

1. A method of feeding strip material to a striputilizing machine while providing a variable'reserve to allow for intermittent interruptions of the feed-in and withdrawal of the strip while maintaining continuously without interruption the withdrawal and feed-in respectively, comprising forming said strip into a single spiral coil having a fixed number of turns and having its axis vertical, feeding said strip onto the inside of said coil while withdrawing strip from the outside of said coil, defining the maximum and minimum radii which the turns of said coil are allowed to have, the difference between said radii being greater than the radial space occupied by the given number of turns of the coil when those turns are close-packed, and allowing the turns to contract successively, or expand successively, to provide a reserve represented by the difference between the expanded and contracted circumferential lengths of the turns that allows continued withdrawal in the absence of feed-in and continued feed-in in the absence of withdrawal, up to the limit of the number of turns present.

2. A strip accumulator for carrying out the method of claim 1 comprising a table for supporting a spiral coil of strip with its axis substantially vertical and provided with means for rotating the turns of the coil about said axis, feed-in means for guiding the incoming strip onto the inside of said coil and withdrawal means for with- I drawing strip from the outermost turn of said coil, means defining a maximum limit on the radius of the coil and means defining a minimum limit on the radius of the coil.

3. The strip accumulator set forth in claim 2 carrying a coil of strip of which the number of turns occupies a radial width, when close-packed, which is substantially less than the difference between said maximum and minimum radii.

4. The strip accumulator set forth in claim 2 wherein said table comprises a plurality of supporting rollers extending radially from said axis, and means for driving at least one of said rollers to form said means rotating the turns of the coil.

5. The strip accumulator set forth in claim 4 wherein said supporting rollers are of uniform diameter along their operative lengths.

6. The strip accumulator set forth in claim 4 wherein the radially innermost ends of said supporting rollers are higher than their radially outermost ends, whereby to define a table of obtuse-angled conical shape.

10. The strip accumulator set forth in claim 4 including movable means for raising the inner turns of said coil clear of said supporting rollers at will, and urging those turns radially outwards.

11. The strip accumulator set forth in claim 2 wherein said feed-in means comprise an arm capable of swinging movement about a vertical axis clear of said table and guide means on the free end of said arm. 

1. A method of feeding strip material to a strip-utilizing machine while providing a variable reserve to allow for intermittent interruptions of the feed-in and withdrawal of the strip while maintaining continuously without interruption the withdrawal and feed-in respectively, comprising forming said strip into a single spiral coil having a fixed number of turns and having its axis vertical, feeding said strip onto the inside of said coil while wIthdrawing strip from the outside of said coil, defining the maximum and minimum radii which the turns of said coil are allowed to have, the difference between said radii being greater than the radial space occupied by the given number of turns of the coil when those turns are close-packed, and allowing the turns to contract successively, or expand successively, to provide a reserve represented by the difference between the expanded and contracted circumferential lengths of the turns that allows continued withdrawal in the absence of feed-in and continued feed-in in the absence of withdrawal, up to the limit of the number of turns present.
 2. A strip accumulator for carrying out the method of claim 1 comprising a table for supporting a spiral coil of strip with its axis substantially vertical and provided with means for rotating the turns of the coil about said axis, feed-in means for guiding the incoming strip onto the inside of said coil and withdrawal means for withdrawing strip from the outermost turn of said coil, means defining a maximum limit on the radius of the coil and means defining a minimum limit on the radius of the coil.
 3. The strip accumulator set forth in claim 2 carrying a coil of strip of which the number of turns occupies a radial width, when close-packed, which is substantially less than the difference between said maximum and minimum radii.
 4. The strip accumulator set forth in claim 2 wherein said table comprises a plurality of supporting rollers extending radially from said axis, and means for driving at least one of said rollers to form said means rotating the turns of the coil.
 5. The strip accumulator set forth in claim 4 wherein said supporting rollers are of uniform diameter along their operative lengths.
 6. The strip accumulator set forth in claim 4 wherein the radially innermost ends of said supporting rollers are higher than their radially outermost ends, whereby to define a table of obtuse-angled conical shape.
 7. The strip accumulator set forth in claim 4 wherein the relative heights of the radially innermost and radially outermost ends of said supporting rollers are adjustable.
 8. The strip accumulator set forth in claim 2 wherein said means defining the minimum limit on the radius of the turns of the coil comprise a ring of rollers.
 9. The strip accumulator set forth in claim 8 wherein said ring of rollers is adjustable radially.
 10. The strip accumulator set forth in claim 4 including movable means for raising the inner turns of said coil clear of said supporting rollers at will, and urging those turns radially outwards.
 11. The strip accumulator set forth in claim 2 wherein said feed-in means comprise an arm capable of swinging movement about a vertical axis clear of said table and guide means on the free end of said arm. 